Sit on a bench or the bottom of a slide with your arms at your sides. Lean back slightly, and then bend your knees and pull them towards your chest, tightening your abs to balance yourself on the slide.

Then extend your legs out straight in front of you.

Modification for beginners: Do everything above except do not extend your legs out as straight. Keeping more bend in the knees on the extension part of this exercise will make this exercise easier.

Do as many repetitions as you can in one minute, with good form, and then jog or walk around the playground for 3 minutes.